(iii) Which is not a basic flux ?

Options

A. `CaCO_(3)`
B. `CaO`
C. `SiO_(2)`
D. None of these

Explanation

To determine which substance is not a basic flux, we need to understand the concept of fluxes in metallurgy.

### Step-by-Step Solution:

1. **Understanding Flux**: Flux is a substance added during the extraction of metals to help remove impurities (gangue) from the ore. The flux combines with the gangue to form a slag, which can be easily removed.

2. **Types of Fluxes**: Fluxes can be classified into two categories:
- **Basic Fluxes**: These are compounds that can react with acidic impurities. Common basic fluxes include calcium oxide (CaO) and magnesium oxide (MgO).
- **Acidic Fluxes**: These are compounds that can react with basic impurities. A common example is silicon dioxide (SiO2).

3. **Identifying the Options**: In the context of the question, we need to evaluate the given options to identify which one is not a basic flux.
- Calcium carbonate (CaCO3) is a basic flux.
- Calcium oxide (CaO) is also a basic flux.
- Silicon dioxide (SiO2) is an acidic flux.

4. **Conclusion**: Among the options, silicon dioxide (SiO2) is not a basic flux; it is classified as an acidic flux. Therefore, the answer to the question is SiO2.

### Final Answer:
**Silicon dioxide (SiO2) is not a basic flux.**

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